My 1998 Bravada started making a tapping/clunking sound, I bought the Haynes manual and have changed out the spark plugs, and checked the rocker arms with no luck. Do you have any ideas of what could be causing this. My oil pressure is good but, the thing is had it changed by someone else about 2 wks ago and drained some out to add an addative recomended by Auto Parts, and the oil was black? The engine very clean & 1 previous owner took very good care of her - she's a keeper - 178990 miles. Any Ideas, before I change the engine